<?php
if(isset($_GET['upload']) && $_GET['upload'] == 'img'){
//二进制数据流
$data = file_get_contents ( 'php://input' ); // 不需要php.ini设置，内存压力小
if(empty($data)){
$data = gzuncompress ( $GLOBALS ['HTTP_RAW_POST_DATA'] ); // 需要php.ini设置
}
if(imagecreatefromstring($data) == false){
exit('图片已损坏');
}
$filename=time().'.png';
$ret = file_put_contents($filename, $data, true);
exit('http://'.$_SERVER['HTTP_HOST'].'/'.$filename);
}
?>
<!DOCTYPE html>
<html>
<head>
</head> <body> <div id="main">
<h1>使用canvas在前端压缩图片实例页面</h1>
<div id="body">
<div id="effect" class="part">
<h3>效果（400x400限制）：</h3>
<div class="show">
<div class="demo">
<p><input id="file" type="file" accept="image/gif, image/png, image/jpg, image/jpeg"></p>
<p id="log"></p>
</div>
</div>
</div> </div>
</div> <script>
// 写log方法，演示辅助，与主逻辑无关
var log = function (info) {
document.getElementById('log').innerHTML += (info + '<br>');
}; var eleFile = document.querySelector('#file'); if (window.FormData) {
// 压缩图片需要的一些元素和对象
var reader = new FileReader(), img = new Image(); // 选择的文件对象
var file = null; // 缩放图片需要的canvas
var canvas = document.createElement('canvas');
var context = canvas.getContext('2d'); // base64地址图片加载完毕后
img.onload = function () {
// 图片原始尺寸
var originWidth = this.width;
var originHeight = this.height; log('图片原尺寸是：' + [originWidth, originHeight].join('x')); // 计算出目标压缩尺寸
var maxWidth = 400, maxHeight = 400; // 目标尺寸
var targetWidth = originWidth, targetHeight = originHeight; if (originWidth > maxWidth || originHeight > maxHeight) {
// 图片尺寸超过400x400的限制
if (originWidth / originHeight > maxWidth / maxHeight) {
// 更宽，按照宽度限定尺寸
targetWidth = maxWidth;
targetHeight = Math.round(maxWidth * (originHeight / originWidth));
} else {
targetHeight = maxHeight;
targetWidth = Math.round(maxHeight * (originWidth / originHeight));
} log('超过400x400的限制，图片大小限制为' + [targetWidth, targetHeight].join('x'));
} else {
log('图片尺寸较小，不压缩');
} canvas.width = targetWidth;
canvas.height = targetHeight; // 清除画布
context.clearRect(0, 0, targetWidth, targetHeight); // 图片压缩
context.drawImage(img, 0, 0, targetWidth, targetHeight); log('图片blob二进制形式ajax上传，当前进度<span id="percent"></span>');
// 转为blob并上传
canvas.toBlob(function (blob) {
// 图片ajax上传
var xhr = new XMLHttpRequest();
// 显示进度的元素
var elePercent = document.getElementById('percent');
// 上传文件名
var filename = encodeURIComponent(file.name).replace(/%/g, ''); // 上传中
xhr.upload.addEventListener("progress", function(e) {
elePercent.innerHTML = Math.round(100 * e.loaded / e.total) / 100 + '%';
}, false); // 文件上传成功或是失败
xhr.onreadystatechange = function(e) {
if (xhr.readyState == 4) {
if (xhr.status == 200) {
// 100%进度
elePercent.innerHTML = '100%'; // 显示上传成功后的图片地址
var response = xhr.responseText; if (/^http/.test(response)) {
//response = response.split(filename)[0] + filename;
log('图片上传成功，地址是：<a href="'+ response +'" target="_blank">'+ response +'</a>');
} else {
log(response);
}
}
}
}; // 开始上传
xhr.open("POST", '?upload=img', true);
xhr.setRequestHeader("X_FILENAME", filename);
xhr.send(blob);
}, file.type || 'image/png');
}; // 文件base64化，以便获知图片原始尺寸
reader.onload = function(e) {
// 图片尺寸
img.src = e.target.result;
};
eleFile.addEventListener('change', function (event) {
file = event.target.files[0]; if (file.type.indexOf("image") == 0) {
log('已选择图片'+ file.name +'，大小为'+ Math.round(1000 * file.size / (1024*1024)) / 1000 +'M。'); reader.readAsDataURL(file);
} else {
log('选择的文件非图片，到此为止。');
}
});
}
</script>
</body>
</html>
效果图（canvas压缩图片会失真）：
